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Old 01-03-2009, 08:11 PM   #1
1000000to1
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speed sensor buffer

Does anyone know EXACTLY where this is on a 98 GMC, I know it is in the glove box area but can't see and don't want to dismantle the truck to find it. I can't find anything on the net other than it is somewhere around there, and the stupid manual I bought don't show it either.
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Old 01-04-2009, 12:09 AM   #2
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Re: speed sensor buffer

i believe the speed sensor buffer applies to the pre 95 trucks. The VSS reports directly to the ECM which is mounted under the hood on the drivers fender.

I'm looking at the wiring diagram for the 96-98 5.0/5.7 and it shows the VSS straight to the ECM
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Old 01-04-2009, 01:23 AM   #3
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Re: speed sensor buffer

Quote:
Originally Posted by bwood View Post

I'm looking at the wiring diagram for the 96-98 5.0/5.7 and it shows the VSS straight to the ECM

That's how my 97 is ran, Then leaves the ECM to the fuse/relay panel next to the ECM then from there through the firewall to the cluster.


1000000to1,

I seen your thread with your speedo problems, I have the same problem with my 97. I loose speedo, and ABS light comes on and cruise quits. Mines a stick but I can see it affecting your shifts since the speedo isn't comprehending vehicle speed. I went through the same testing you are doing, I talked to my local Chevy dealer about mine and he told me the ECM had nothing to do with the speedo (I didn't know at the time it did, I had just bought the truck) so I bought a rebuilt cluster from them @ $350 and that didn't fix the problem.

I tested and re-tested everything and couldn't find the problem so took it to the dealer. They said $65 check-out fee, Three hours later he came in the waiting room and said my ECM was bad @ $550 but didn't have one in stock. He went on to say he had a used one from a wrecked truck he would give me with no warranty if I paid the three hours labor @ $295....

I told them if it got it working put it in, It worked for a whopping 12 miles and quit.....

Now after $645 I got to messing around with the fuse/relay panel next to the ECM and it started working again then quit, I have found if I lay my hand on this panel and give it a quick but light pull toward the fender it will start working again until I hit a bump just right. I have repeated this over a dozen times (haven't taken time to check it) to get it working, My job for tomorrow is removing this fuse/relay panel from the wheel well and checking ALL connections and wires for shorts.


The moral of this story is;

Don't think your local dealership won't rape you either, I'm in the hole $645 and still hunting the problem but atleast I know the general area to look now.


Good Luck
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Last edited by Restrorob; 01-04-2009 at 01:26 AM.
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Old 01-04-2009, 05:05 PM   #4
1000000to1
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Re: speed sensor buffer

You have to love electrical problems, I had a snowmachine that cost me around the 2 grand mark twice for the dealer to figure out problems, looks like this will be simular. Thanks for the help, back off to the garage to try and find again.
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Old 01-14-2009, 01:13 PM   #5
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Re: speed sensor buffer

Hey guys, I am going thru the same problem on my 97 sierra 3500. There is no buffer behind my glove box. i am now pretty sure that the wiring from the vss goes STRAIGHT to the ECM. I got that corrisponding answer from a tech. My truck was shifting incorrectly, I unplugged the VSS at the transfer case so now the truck shifts in its default mode. After I physically verify the wires good I will be replacing the ECM.I am glad I found this site..no help @ gm-trucks thanks troc
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